A method of the art for manufacturing a seat comprising a foamed body having various hardnesses and an air-permeable surface material connected in one with the foamed body is shown in FIGS. 5 and (this method is described in a Japanese patent application filed on Jul. 1, 1996,). This manufacturing method is carried out as follows.
A first foamed body 51 as a base part has been molded in advance. As shown in FIG. 5, firstly, a liquid foamable mixture 52 such as a polyurethane foam is introduced and layered on the first foamed body 51. A thickness of the liquid foamable mixture 52 layered on the first foamed body 51 is generally leveled over a flat part 51' of the first foamed body 51. An air-permeable surface material 54 is composed of an upper part 55 and side parts 56, 56' stitched on both sides of the upper part 55. The upper part 55 of the surface material 54 is placed on the mixture 52 layered on the first foamed body 51, and the side parts 56, 56' are positioned on both side surfaces of the first foamed body 51.
A part of the mixture 52 which contacts with the flat part 51' of the first foamed body 51 is impregnated into the first foamed body 51 through the flat part 51' thereof, so that an impregnated layer is formed.
Then, a pressure applying die 60 is positioned above the surface material ( see FIG.6 ) . This pressure applying die 60 is hollowed, and a plurality of suction holes 61, 62 are provided adjacent to ascending parts formed on a surface 60' of the die 60. Descending parts formed on the seat are molded by those ascending parts of the die 60. The pressure applying die 60 is moved downward and an inner space thereof is simultaneously pumped out through the suction holes 61, 62. Both the liquid foamable mixture 52 and the surface material 54 are pressed and compressed between the pressure applying die 60 and the first foamed body 51 when the mixture 52 has completed a gas reaction thereof but is still in a visco-elastic flowing condition.
As described above, the low air-permeable impregnated layer is formed in the foamed body 51 which contacts with the mixture 52 layered thereon, so that the whole becomes a low air-permeable composite material, and when the inner space of the pressure applying die 60 is pumped out during the pressing and compression, the pumping force acts on the low air-permeable composite material, so that a large pressure difference is produced between an inside of the composite material and a pumping side thereof. Thus, even though a molding surface of the pressure applying die has a complicated shape, the liquid foamable mixture in the visco-elastic flowing condition is attracted toward the pumping side with the surface material while a reactive force caused by the pressing and compression acts thereto, so that the surface material 54 is pushed onto the pressure applying die so as to follow the molding surface 60' of the pressure applying die 60. A portion which can be molded and shaped in a desired shape corresponding to a shape of a die by sucking the liquid foamable mixture with the surface material as described above is hereinafter referred to as a sucked and molded portion.
Then, the liquid foamable mixture 52 is changed (or cured) into a solid condition ( a resin like condition ) , so that the second foamed body 51 having a desired resiliency can be formed, and simultaneously, a back surface of the surface material 54 is connected in one with an upper side of the second foamed body 51 and the first foamed body is connected in one with a lower side thereof.
If a hardness of the first foamed body and that of the second foamed body are adjusted, respectively, or if the compressibility and the like of the second foamed body is adjusted when carrying out the pressing and compression, then a seat having various hardnesses provided in the surface material can be manufactured.
As described above, according to this method of the art, a seat with an air-permeable surface material can be manufactured without use of a lower die, such that the first foamed body is connected in one with the second foamed body and even though a molding surface of a pressure applying die has a complicated shape, the surface material can be connected with the second foamed body and can have a shape corresponding to the molding surface of the pressure applying die.
However, since the liquid foamable mixture in a visco-elastic flowing condition is introduced and layered thereon in level, the mixture is uniformly resinified (cured) , so that the layered mixture can be easily compressed uniformly, and, as described above, since the impregnated layer is formed, the whole of the mixture 52 and the first foamed body 51 results in a low air-permeable composite material, so that the whole of the first foamed body 51 is pushed toward the pressure applying die 60 by the pressure difference produced by the suction. That is, as indicated by a broken line shown in FIG. 6, the first foamed body 51 is lifted upward and moved toward the mixture 52 so as to crush the whole of the mixture 52 and so as to thin the thickness thereof, and then, when the mixture is cured, it may make the tactile feeling of a seat surface worse.
If the sucking force is reduced to avoid such a lift, a molding of the mixture by the suction can not be carried out sufficiently.
Also, when manufacturing a seat having a complicated shape and deeper descending parts, that is, when manufacturing such a seat by use of a pressure applying die having a complicated molding surface shape, it is required to suck strongly to carry out sufficient molding by the suction. However, the first foamed body 51 is lifted more strongly upward and moved toward the mixture 52, and as a result, the mixture 52 is crushed more.
Moreover, if the mixture is cured when the first foamed body is lifted upward, the first foamed body is recovered to its original shape by a resiliency of the first foamed body after completing the molding, and as a result, a part of the second foamed body desired to be flat is deeply depressed, and thus, a seat having a desired shape can not be manufactured.
As described above, when molding a seat shape, the mixture 52 should not be compressed by the lift of the first foamed body. (The mixture at such a portion is hereinafter referred to as a portion not to be compressed.)
The present invention is made in order to solve those problems, and an object thereof is to provide a seat and a method for manufacturing the seat wherein the seat has a surface shape corresponding to a molding surface of a molding die, a surface material of the seat is connected in one with a foamed body thereof and a tactile feeling of a surface of the seat is improved.
Another object of the present invention is to provide the seat and a method for manufacturing the seat wherein an air-permeable surface material can we used for the seat described above.
Still another object of the present invention is to provide the seat and a method for manufacturing the seat wherein an upper layer of the seat which contacts a person is soft and a lower layer thereof which supports a weight of the person is hard.
Yet still another object of the present invention is to provide the seat and a method for manufacturing the seat wherein the hardness of the upper layer is partially different.